1. Field of the Invention
The use of conductive fibers in tufted carpets as a means for dissipating static charge is the field of this invention.
2. Prior Art
There are many methods for dissipating static charges in tufted carpets by using a conductive primary backing. Examples of U.S. patents disclosing conductive fibers which can be used in the primary backings of the prior art and the secondary backing of this invention are: U.S. Pat. Nos. 3,969,559 (1976), 3,836,422 (1974), 3,806,401 (1974), 3,778,331 (1973), 3,713,960 (1973), 3,690,057 (1972), 3,669,736 (1972), 3,206,923 (1965), 3,129,487 (1964).
Electrically conductive undercoatings such as in U.S. Pat. No. 2,302,003 (1942) have not achieved widespread commercial acceptance because: (1) the bonding strength of latex compositions is significantly reduced whenever fillers such as conductive carbon black or other fillers to make a conductive coating are present; (2) to make up for any lessening of latex bond strength excess film forming polymer must be used, which significantly increases manufacturing costs; (3) in the case of conductive carbon black as filler, there are adverse aesthetic consequences from binder and filler bleedthrough; (4) the process of coating with filled conductive latex compositions have many manufacturing difficulties; and (5) such coatings, as expressly pointed out in U.S. Pat. No. 2,302,003, must contact whatever conductive pile loops are used in order to dissipate adequately static charge.
It is to be noted that the conductive pile yarns are in general required in order to maintain a kilovolt potential determined according to AATCC 134 (1969) below about 4.5 kilovolts (KV) regardless of the further means used to dissipate such static charge.
Another method for producing tufted carpets which prevents high static charge buildup is to modify the otherwise nonconductive primary backing by incorporating conductive fibers directly into the primary backing either as components in the woven or nonwoven web or as part of a fleece layer needle-bonded thereto. Examples of such art are U.S. Pat. Nos. 3,955,022 (1976), 3,900,,624 (1975), 3,806,401 (1974), 3,713,960 (1973) and 3,639,807 (1972). Modification of the primary backing is a commercially accepted method, but unfortunately, necessarily gives rise to a significant increase in inventory due to the variety of primary backing colors and/or constructions which must be duplicated both as conductive and nonconductive backings.
Another method for dissipating a charge from a tufted carpet other than by directly modifying the primary backing is disclosed in U.S. Pat. No. 3,728,204 (1973). In U.S. Pat. No. 3,728,204, an aluminum foil is laminated directly to the loop side of a tufted carpet, wherein the foil is positioned so as to be in direct electrical conductive contact with respect to the yarn projecting from said loop side.
Foil lamination is not extensively used commercially probably because of (1) the production problems in uniformly laminating a foil to the loop side of a tufted carpet, which may explain the use in U.S. Pat. No. 3,728,204 of a pin roller to pierce the metal foil so as to make contact with the pile loops, and (2) the undesirable aesthetics arising from having a highly reflective substrate. It is important to emphasize that as taught in U.S. Pat. No. 3,728,204 there is a requirement that before static charge can be dissipated satisfactorily an electrical contact between the conductive pile and the foil must be present because such a limitation has surprisingly been found not to be required by this invention.
It is an object of this invention to avoid static charge buildup in tufted carpets of kilovolts in excess of about 4.5 KV as measured according to AACCT 134 (1969) by means of a conductive secondary backing.
It is an object of this invention to provide a conductive secondary backing which overcomes all of the problems and limitations of prior art methods of lessening static charge buildup while being capable of dissipating static charges to a value in kilovolts of less than about 4.5 KV.
Other objects of this invention are clear from the Specification.